The present application is based on Japanese Patent Applications Nos. 2001-135638, 2001-226858, 2002-33713, 2002-33714 and 2002-33715, which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a centrifugal dehydrating technology for removing a liquid such as a cleaning liquid adhered to a workpiece with a substantially rectangular plane (hereafter referred to also as a pallet or the like) such as a pallet or a tray or container similar thereto by the action of a centrifugal force.
2. Description of the Related Art
Conventionally, in a case where a pallet or the like formed of a resin is centrifugally dehydrated, it has been the general practice to effect centrifugal dehydration in a horizontal state in a state in which the pallet or the like is being conveyed on a conveyor. However, there are many cases where the pallet or the like is provided with a multiplicity of ribs to increase the strength, and a multiplicity of recessed portions are formed by those ribs, so that the actual situation has been such that the cleaning liquid gathered in the recessed portions cannot be easily removed even if centrifugal dehydration is performed. Accordingly, concerning the centrifugal dehydration of the pallet, a technique has been disclosed in which the pallet is rotated in an upright state (Japanese Utility Model Publication No. Hei. 6-52973). In this case, the cleaning liquid remaining in the recessed portions can be removed efficiently. However, in the case of this conventional technique, the center is liable to be offset at the time of holding the pallet, so that there has been a problem in that if the pallet is rotated as it is, the pallet becomes unstable due to an imbalance; and there is a large danger. Due to these circumstances, the holder has tended to be complex and large in size so as to hold the pallet securely. In addition, the types of pallets are very numerous, and it has been difficult to jointly use the same apparatus for the pallets of different sizes.
The present invention has been devised in view of the above-described conventional technical situation, and its object is to provide a centrifugal dehydration apparatus for a pallet or the like which, at the time of holding the pallet or the like, makes it possible to easily locate the center of gravity of the pallet or the like on the axis of rotation and is capable of easily suppressing the runout due to the centrifugal force.
In the invention, to overcome the above-described problems, a workpiece with a substantially rectangular plane is held an a diagonal line of its substantially rectangular plane by a pair of holders which are rotated by a rotator, and the diagonal line of the workpiece is aligned with an axis of rotation. Since the center of gravity of the workpiece is generally located on its diagonal line, the center of gravity of the workpiece is located on the axis of rotation according to the above-described structure. Accordingly, in accordance with the invention, it is possible to easily suppress the runout due to the centrifugal force. It should be noted that the alignment of the diagonal line of the workpiece with the axis of rotation, which is referred to herein, is not to be construed in a strict sense, and it suffices if it is possible to suppress the runout due to the centrifugal force to such an extent as to cause no hindrance by obviating an imbalance in rotation by substantially aligning the diagonal line of the workpiece with the axis of rotation. If the pair of corner portions of the workpiece are held on its diagonal line by the pair of holders, the diagonal line of the workpiece can be easily aligned with the axis of rotation. It should be noted that the direction of rotation of the workpiece may be changed over between forward rotation and reverse rotation, or the frequency of changeover may be set to two times or more. In addition, after the workpiece is subjected to cleaning in an upright state such that one edge thereof is set as a bottom, the workpiece may be tilted such that a corner portion thereof is set as a bottom, and centrifugal dehydration may be effected in the tilted state. Furthermore, the pair of holders may be each arranged to be capable of tilting in correspondence with abutment against two adjacent edge portions with each of the corner portions located therebetween when the pair of corner portions of the workpiece are respectively held by the pair of holders, and there may be further provided a supporting mechanism for supporting the two edge portions with the corner portion of a bottom of the workpiece located therebetween and a transfer mechanism for transferring the supporting mechanism.
Incidentally, the present invention may be employed to centrifugally dehydrate a planar workpiece such as a planar pallet, however, the shape of the workpiece is not limited to this. For example, the shape of the workpiece may be rectangular solid, cube, or the like. xe2x80x9cA workpiece with a substantially rectangular planexe2x80x9d may be a workpiece having a contour with a substantially rectangular plane viewed from at least one direction. This type of workpiece has at least a pair of corner portions to be held when dehydrated.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.